ET : N - Synaptic Transmission Flashcards
what is synaptic transmission
the process of transferring information between neurons or between neurons and muscle fibres
synaptic transmission occurs between neurons through either of which two things?
chemical synapses
or
electrical synapses (via gap junctions)
where is the neuromuscular junction
outside the brain in skeletal muscle
describe the process of using the neuromuscular junction as a model of (excitatory) synaptic transmission
- action potential arrives to presynaptic terminal
- action potential invades terminal and activates voltage-gated Ca2+ channels increasing influx of Ca2+
- release of transmitter (acetylcholine) by exocytosis
- reaction of transmitter with post synaptic receptors
- activation of ligand-gated ion channels
- post-synaptic EPP and action potential
what is the ionic mechanism of end-plate potentials (EPP)
transient opening of ion channels selective to both Na+ and K+ (non-selective cationic channels)
end-plate potential is always
suprathreshold
end-plate potential is always suprathreshold which means
always triggers an action potential
when EPP triggers AP, where does it go
transmitted along the muscle fiber
what are neurotransmitters
chemical messengers that open (or sometimes close) ion channels, and lead to depolarisation or hyperpolarisation of post-synaptic membrane
what are the two types of chemical synapses in CNS
excitatory synapses and inhibitory synapses
what do excitatory synapses evoke
depolarisation of the postsynaptic membrane called excitatory postsynaptic potential (EPSP)
what do inhibitory synapses evoke
hyperpolarisation of the postsynaptic membrane called the inhibitory postsynaptic potential (IPSP)
what is the ionic mechanism of EPSPs (and what does this do to the RMP?)
the transient opening of channels selective for Na+, K+ and sometimes Ca2+
this shifts Vm of RMP towards the threshold for generation of an AP
what is the ionic mechansim of IPSPs
often through the transient opening of K+ channels
what is the main neurotransmitter of EPSPs
glutamic acid or ACh
what is the main neurotransmitter of IPSPs
GABA or glycine
what causes IPSPs
increase of cell membrane permeability to K+ function by hyperpolarising the cell membrane
IPSPs work ________________ of EPSPs and thus IPSPs do not need to be evoked before or after the occurrence of EPSPs
independently
does synaptic transmission have a delay
yes a very minor one
how are neurotransmitters classified
based off of chemical structure